1. Field of the Invention
The present invention relates to a supporting plate which is used when a substrate such as a semiconductor wafer is thinned, and also relates to an apparatus and a method for stripping the supporting plate from the semiconductor wafer.
2. Description of the Background Art
There is a continuing need to make IC cards and cell phones thinner, smaller, and lighter. In order to satisfy this need, semiconductor chips to be incorporated therein must be thin. Although at present the thickness of a wafer which forms a semiconductor chip is 125-150 μm, it is expected that the thickness of a semiconductor wafer must be 25-50 μm for a next generation of chips.
An example of a conventional method for thinning a semiconductor wafer is shown in FIG. 8. Specifically, a protecting tape is attached to a surface (A-surface) of a semiconductor wafer on which a circuit (element) has been formed. The wafer is turned over, and the rear surface (B-surface) of the semiconductor wafer is ground by a grinder to make the wafer thinner. The B surface of the semiconductor wafer which has been thinned is fixed onto a dicing tape retained by a dicing frame, and the protecting tape covering the surface (A-surface) of the semiconductor wafer on which a circuit (element) has been formed is stripped in this state. Next, the wafer is cut into each chip by a dicing device.
The above-mentioned method has been disclosed in Document 1. According to Document 1, the heat-resistant protecting tape is stripped from the thinned semiconductor wafer by using a strong adhesive tape bonded to one end of the protecting tape.
Document 2 has disclosed that a protecting base obtained by immersing a ladder-type silicone oligomer in an aluminum nitride-boron nitride porous sintered material is used instead of a protecting tape, and the protecting base and a semiconductor wafer are bonded by using a thermoplastic film. Document 2 also mentions that they are immersed in pure water at 80° C. for 3 hours before stripping.
Document 3 has disclosed that a protecting base is made of a material having the same thermal expansion coefficient as a semiconductor wafer such as alumina, aluminum nitride, boron nitride, or silicon carbide.
Also, Document 3 has proposed a method in which the protecting base and the semiconductor wafer are bonded by using a thermoplastic resin such as polyimide, the semiconductor wafer is thinned by a grinder, and thereafter stripping is performed by immersing in water, amine, or a mixed solution of water and amine, or by using steam.    [Document 1] Japanese Patent Application Publication No. 2002-270676    [Document 2] Japanese Patent Application Publication No. 2002-203821    [Document 3] Japanese Patent Application Publication No. 2001-77304
In the above-mentioned techniques, since it is difficult for a solvent to enter between the supporting plate (protecting tape) and the semiconductor wafer when the supporting plate (protecting tape) is stripped from the semiconductor wafer, it takes too much time to strip the supporting plate from the semiconductor wafer.
Also, the thermoplastic film bonding the support plate (protecting tape) and the semiconductor wafer often fails to completely dissolve, and tends to be left in a state of sticking to either the support plate or the semiconductor wafer.
If an adhesive is left as described above, cracking or chipping of the semiconductor wafer easily occurs at the time of stripping.
In order to solve the above problem, the present applicant has proposed a supporting plate in which a plurality of penetrating holes are provided in the thickness direction of the supporting plate. FIG. 9 explains a method for stripping this supporting plate.
According to this method, a solvent supplying plate 102 is laid onto the upper surface of a supporting plate 100 via an O-ring 101. Next, a solvent is supplied from a solvent supplying pipe 103 to a space S surrounded by the supporting plate 100, the O-ring 101 and the solvent supplying plate 102. The solvent passes through penetrating holes 104 formed in the supporting plate 100, dissolves and removes an adhesive layer 105.
With the method of using a supporting plate in which a plurality of penetrating holes are provided, it is possible to securely remove an adhesive in a short period of time. However, another problem arises.
As shown in FIG. 10, the solvent leaks from the periphery of the supporting plate to the outside, and the solvent drops onto the dicing tape, which results in a deterioration of the dicing tape in a short period of time.
Further, efficiency of stripping is bad because part of a new solvent supplied to the space S is withdrawn without being utilized.
Furthermore, even if the adhesive is completely dissolved, if a finger or the like is used as a device for stripping the semiconductor wafer from the supporting plate, there is a strong likelihood that the circuit-formed surface of the semiconductor wafer will be damaged.
In order to solve the above-mentioned problems, an object of the present invention is to provide a supporting plate which makes it possible to easily strip the supporting plate from a substrate in a short period of time after thinning the substrate, and an apparatus and a method for stripping the supporting plate.